With homes sitting just beyond the fence line and even closer to the runway in some spots, Boulder Municipal Airport is now working against the clock to bring in unleaded aviation fuel by Dec. 31, 2026. A newly filed transition plan sketches out how the switch could start, but leaves big questions hanging over which fuel will be chosen, what new tanks or pumps might be needed and who ultimately picks up the tab. City officials say the plan is a living document that will be revisited as fuel certifications, costs and grant opportunities shift over the next several years.
According to the Boulder Reporting Lab, the draft calls for unleaded avgas to be available for retail sale at the airport by the end of 2026. It leans on incentives, including reimbursement for supplemental type certificates and state subsidies that could soften the blow of higher per-gallon prices for pilots. The document also floats a longer-term option to install a roughly 10,000-gallon self-service tank, although it stops short of choosing a specific unleaded product or laying out a final budget for the upgrade.
State law and money behind the push
The city’s move is not happening in a vacuum. Colorado’s HB24-1235 requires five airports, including Boulder, Longmont/Vance Brand, Centennial, Rocky Mountain Metropolitan and Erie, to submit phase-out plans by Jan. 1, 2026, and creates a grant program to help pay for the change. As outlined by the Colorado Department of Transportation, the state has identified discretionary funds and technical guidance meant to help airports cover the cost of tanks, fuel trucks and pilot certification paperwork tied to unleaded fuel.
Who would sell the fuel
On the ground, any switch hinges on the airport’s fixed-base operator, Journeys Aviation, which currently handles on-site fuel sales. The city has not nailed down the total transition cost, and officials say the bill is likely to be split among airport revenues, state grants and investments by the operator as the project moves from planning to construction.
Which fuels are on the table
Several unleaded contenders are in play. Airports can already buy lower octane unleaded blends, while high octane candidates are being developed to replace 100LL across the piston fleet. Centennial Airport, for example, has been selling Swift Fuels’ UL94 and pairing that with subsidies and STC reimbursements to speed up adoption. At the same time, national trade groups and industry coverage report that manufacturers such as GAMI and Swift are working on higher octane, fleet wide unleaded solutions. Each option comes with its own mix of technical limits and distribution hurdles, so airports like Boulder are trying to balance availability, cost and what local pilots are willing to use.
Health evidence and community worry
Behind the policy talk is a health concern that has been getting harder to ignore. A peer-reviewed analysis in PNAS Nexus linked higher blood lead levels in children to living near and downwind of piston engine airport operations, and those findings have already pushed some counties to restrict sales of leaded avgas. That research, combined with warnings from public health experts about lead’s impact on brain development, is shaping how Boulder residents and officials judge the urgency and scope of any airport fuel transition.
Legal and regulatory constraints
Boulder’s options are also framed by federal rules. The city dropped its lawsuit against the FAA in November 2025 after a judge dismissed the case, and leaders now say the airport is operating under its existing federal obligations. Nationally, the FAA and the industry’s EAGLE initiative have set a goal of eliminating leaded avgas by 2030. At the same time, recent FAA grant assurance guidance requires airports that sold 100LL in 2022 to keep offering it until an FAA approved unleaded replacement is widely available or until Dec. 31, 2030, as explained in industry reporting and agency materials.
What to watch next
In the near term, the drama will center on which unleaded fuel Boulder chooses, whether the city commits to that proposed 10,000-gallon self-service tank and how much state grant money ultimately lands at the airport to cover infrastructure and STC costs. The draft plan says officials will seek feedback from tenants and the broader public as the schedule evolves, and Colorado’s grant history shows the state is already backing transition projects at other airports to move things along. For more details, see the city’s plan and state guidance.
